LA3JJ Antennas
Magnetic Loops II
I have been tempted by Ross to make a two turn loop. I used PexAl tubes from my
local plumber. Only dimension he had was 16mm. I used the tube just as it comes
from the coil, no bending or stretching. That gave me a diameter of about 77 cm.
First I measured its self resonance, it was ca 17 MHz. I wanted to make a single
band antenna. Naturally I choose the 20 m band. With the dimensions at hand
lower frequencies would mean lower efficiency. I might have cut it a bit shorter and
made a 70 cm diameter loop for the 17 m band, that will be another day.
One good thing with multi turn loops is that you can fine-tune them without
adjusting the trombone capacitor. My dream is to have an all weather antenna, so
the trombone must be air tight, and its value adjusted once and epoxy glued.I used
some "bathroom tube clamps" as spacers.
I have been tempted by Ross to make a two turn loop. I used PexAl tubes from my
local plumber. Only dimension he had was 16mm. I used the tube just as it comes
from the coil, no bending or stretching. That gave me a diameter of about 77 cm.
First I measured its self resonance, it was ca 17 MHz. I wanted to make a single
band antenna. Naturally I choose the 20 m band. With the dimensions at hand
lower frequencies would mean lower efficiency. I might have cut it a bit shorter and
made a 70 cm diameter loop for the 17 m band, that will be another day.
One good thing with multi turn loops is that you can fine-tune them without
adjusting the trombone capacitor. My dream is to have an all weather antenna, so
the trombone must be air tight, and its value adjusted once and epoxy glued.I used
some "bathroom tube clamps" as spacers.
I used a program made by DG0KW for calculating the loop.
I just had to go on the air with the antenna against the wall in my living room.
12 stns reported my first wspr call.
This was the best "dx" :
15:42 LA3JJ 14.097131 -22 0 JO59bh 5 N6MZ CN87wn 7364
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